Blindstitch sewing machine

ABSTRACT

This disclosure relates to improvements in a blindstitch sewing machine for blind hemming an edge of a material which is doubly reversely folded. A guide member is provided for supporting the folded material when it is elevated by an associated plunger in position for passage of a needle therethrough. The guide member is in the form of a bent length of wire which is gravity urged to its operative position and is disposed in alignment between a plunger and a cloth retaining finger so as to assure the position of the folded material. The plunger is constructed so that it will oscillate and is in the form of a blade-like member pivotally mounted at one end thereof and resiliently urged towards the associated finger.

1 United States Patent [191 [111 3,747,546 Jurgens 1 July 24, 1973 [54] BLINDSTITCH SEWING MACHINE 2,250,745 7/1941 Buono 112/178 [75] Inventor: Erwin Jurg Stuttgart, Ge y 2,113,107 4/1938 Bowman ll2/l78 [73] Assignee: Union Special Maschinenfabrik Primary ExaminerH. Hampton Hunter GmbH, Stuttgart, Wuerttemberg, Attorney-Charles J. Diller et al. Germany 22 Filed: July 12, 1971 [571 ABSTRACT This disclosure relates to improvements in a blindstitch [211 App! 161517 sewing machine for blind hemming an edge of a material which is doubly reversely folded. A guide member [30] Foreign Application Priority Data. is provided for supporting the folded material when it July 29, 97 G a p 0 37 5 3 5 is elevated by an associated plunger in position for passage of a needle therethrough. The guide member is in [52] US. Cl. 112/178 the form of a bent length of wire which is gravity urged 51 Int. Cl 1105b 1 24 to its Operative position and is disposed in alignment 58 Field of Search 112/178, 176, 177, between a plunger and a cloth retaining finger so as to 112 13 assure the position of the folded material. The plunger is constructed so that it will oscillate and is in the form [56] References Cited of a blade-like member pivotally mounted at one end UNITED STATES PATENTS thereof and resiliently urged towards the associated fin- 1,506,854 9 1924 M'oulton 112/178 2,189,433 2/1940 Mueller 112/178 16 Claims, 10 Drawing Figures PATENIEU Jl1l24'975 3. 747. 546

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INVENTUR ERUHN JURGENS B K fla Ml N fix ATTOQNEYs BLINDSTITCH SEWING MACHINE This invention relates to a blindswitch sewing machine for blind hemming the edge of material which is doubly reversely folded so as to have a generally S- shaped configuration during stitching.

BACKGROUND OF THE INVENTION In the use of blindstitch sewing machines which effect the blind hemming of the edge of cloth, the edge portion of the cloth is reversely folded doubly upon itself to a generally S-shape and the needle of the sewing machine pricks at intervals through the second turned fold of the edge portion when the material is lifted by a plunger. The needle also pricks through the material adjacent the fold through a part of the cloth which had been previously lifted by a second plunger. After sewing, the second turned fold returns to its original position so that the hem seam will lie invisible between the cloth part and its turned over edge.

A basic blindstitch sewing machine of the type discussed above is fully disclosed in the patent to Charles W. Mueller, US. Pat. No. 2,189,433, granted Feb. 6, 1940.

Operators of prior blindstitch sewing machines have found it difficult to achieve an acceptable beginning stitch of the folded material. The folded material may retreat away from the approaching needle as a result of which the stitch will be insufficient or there will be no stitch at all.

SUMMARY OF THE INVENTION In accordance with this invention, movement of the folded material away from the approaching needle is eliminated by fixing the position of the turned fold relative to the path of the needle in a'satisfactory manner by means of efficient guidance.

The guidance of the folded material is achieved by providing a guide element which is positioned above the plunger which lifts the turned fold into the path of the needle, the guide element engaging the turned over fold supporting the turned fold in a position for the needle to prick the same. This guide element is located within the turned fold and together with the usual holddown device which is attached in the customary manner to the pressure plate, holds the turned fold firmly in the desired position so that an even stitching of the turned fold will be achieved. The guide member moreover advantageously functions as auxiliary means in the forming of the second turned fold.

Preferably the guide member consists of a finger attached flexibly on the pressure plate in a manner wherein gravity swings the finger into engagement with a resilient hold-down device carried by the pressure plate. If necessary, the guide member may be more positively held against the hold-down device by the addition of a spring.

The force with which the guide member fits against the hold-down device is less than the spring tension with which the hold-down device is urged in opposition to the plunger. Preferably, the plunger is also mounted for resiliently resisted movement by means of spring tension which is higher than the spring tension of the hold-down device so that the hold-down device to gether with the guide member is forced upwardly by the plunger against its stop.

The flexibly mounted plunger preferably is in the form of a blade-like member which is pivotally carried in a bifurcated part of a base and which is resiliently urged out of the bifurcated part about'its pivot point with there also being means for limiting the outward swinging of pivoting of the plunger.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawings:

IN THE DRAWINGS FIG. 1 is a side elevational view of a blindstitch sewing machine formed in accordance with this invention.-

FIG. 2 is an exploded perspective view of a presser foot or plate incorporating the guide member.

FIG. 3 is an end view of the presser foot.

FIG. 4 is a fragmentary sectional view taken along the line 4--4 of FIG. 3 and shows more specifically the relationship of the components carried by the presser foot.

FIG. 5 is a vertical sectional view taken generally along the line 5-5 of FIG. 4 and shows the relationship of hold-down devices and associated plungers during the initial formation of a stitch in material having a folded hem.

FIG. 6 is a view similar to FIG. 5 and shows the position of the needle wherein it has pricked the folded material after first pricking an adjacent portion of the material.

FIG. 7 is an enlarged fragmentary sectional view showing specifically the cross section of a modified guide member finger and its associated hold-down de- VlCC.

FIG. 8 is a fragmentary vertical sectional view show ing the general details of one of the plungers and the mounting thereof.

FIG. 9 is an end view of the plunger and the support therefor on an enlarged scale.

FIG. 10 is a vertical sectional view taken along the line 10-10 of FIG. 9 and shows the specific details of the mounting of the plunger relative to its base.

Referring now to the drawings in detail, it will be seen that there is illustrated in FIG. 1 a blindstitch sewing machine generally of the customary type, but specially equipped in accordance with this invention. The sewing machine includes a base element 1 whichis provided with a handwheel 2 carried by a main driving shaft 3. The sewing machine also includes an arm 4 extending from the base 1, the arm carrying the sewing tools and their drivingelements. The sewingtools include a needie 5, a looper 6, a presser plate 7 and plungers or ridge forming discs 8 and 9 of which only the plunger 9 is illustrated in FIG. 1, the plunger 8 being illustrated in FIGS. 5 and 6. The plungers or ridge forming discs are mounted in an arm or work apron 10 which supports the cloth being hemmed and which also receives the conventional driving elements for the plungers 8 and 9. The pressure plate 7 carries a pair of resilient holddown devices 11 and 12 of which only the hold-down device 12' is illustratedin FIG. 1, the hold-down device 11 being more specifically illustrated in FIGS. 2, 5 and 6. The hold-down devices 11 and 12 cooperate with the plungers 8 and 9, respectively.

According to the present invention, a guide element, generally identified by the numeral 13, is pivotally mounted relative to the pressure plate 7, and this guide element is in the form of a bent length of wire. The guide element 13 lies between the hold-down device 12 and the associated plunger 9. As will be readily apparent from the foregoing, the guide element 13 is constantly urged towards the holddown element 12 by gravitational forces.

Referring now to FIG. 2 in particular, it will be seen that the presser plate 7 is of a conventional construc tion and is provided at one end thereof with a sleeve portion 14 in which there is adjustably positioned a bushing 15. An eccentric stud 16 is adjustably mounted within the bushing 22 and has pivotally mounted thereon the hold-down device or retainer 11. A spring 17 carried by the eccentric stud 16 resiliently urges the hold-down device 11 towards the presser plate 7 at all times and downward movement of the hold-down device 11 is restricted by its engagement with the presser plate 7.

The presser plate 7 is also provided with a second sleeve portion 18 which is generally aligned with the sleeve portion 14 and which has adjustably mounted therein another eccentric stud 20. The stud 20 has pivotally mounted thereon the hold-down device or crown 12. It is to be noted that the hold-down device 12 has an extension 21 with a threaded bore 22 therethrough. An adjusting screw 23 is threaded through the bore 22 and is engageable with the pressure plate 7 to limit the upward movement of the hold-down device 12.

The adjusting screw 23 has a bore therethrough of which the upper portion is threaded as at 24. A pin 25 projects out of the lower end of the adjusting screw 23 and engages the presser plate 7. The pin 25 is resiliently urged downwardly by means of a spring 26 which reacts against a set screw 27 threaded in the threaded portion 24 of the adjusting screw 23. The spring 26, through the pin 25, resiliently urges the hold-down device 12 downwardly towards the presser plate 7 at all times. Downward movement to the hold-down device 12 is limited either by engagement of the hold-down device 12 with the presser plate or an element carried thereby.

It is to be noted that the adjusting screw 23 is provided with an enlarged peripherally knurled head 28 which is constantly engaged by a spring type retainer 30 that is suitably secured to the extension 21 of the hold-down device 12 by means of screws 31.

It is also to be noted that the presser plate 7 is provided with a needle guide 32 so as to assure the proper positioning of the needle as it passes transversely across the presser plate 7.

It is to be understood that the afore-described components of the presser plate 7 and the hold-down devices 11 and 12 are conventional and in of themselves do not define specific components of this invention.

Referring once again to the construction of the guide 13, it will be seen that the guide is bent of wire and is generally rectangular in outline. The guide 13 includes a first leg 33 which has one free end and one end thereof connected to a leg 34 which extends generally normal to the leg 33 and which may be of a slightly V- shaped outline if desired. Connected to the opposite end of the leg 34 is a leg 35 which extends substantially parallel to the leg 33, but remote therefrom, as is clearly shown in FIG. 4. The leg 35 has integrally connected to the opposite end thereof a leg 36 which extends generally parallel to the leg 34 towards the free end of the leg 33, but is both spaced therefrom and offset from the axis thereof as is clearly shown in FIGS. 2 and 4. The leg 36 is in the form of a finger which functions as a guide and cooperates with both the plunger 9 and the hold-down device 12. The leg or finger 36 terminates in an end portion 37 which is of a tapered construction and is configurated to cooperate with the cloth engaging part of the hold-down device 12, the cloth engaging part of the hold-down device 12 being identified by the numeral 38.

Referring once again to FIG. 2 in particular; it will be seen that the eccentric stud 20 has a bore 40 therethrough in which the leg 33 of the guide element 13 is received for freedom of pivotal movement. The free end of the leg 33 is provided with a suitable stop element 41 so as to retain the leg within the eccentric stud 20. A positioning collar 42 is adjustably mounted on the leg 33 for cooperation with the outer end of the eccentric stud 20 to effect the positioning of the finger 36 so that the tapered end portion 37 thereof will properly seat relative to the portion 38 of the hold-down device 12.

It is also to be noted from FIG. 4 that a major portion of the guide element 13 is disposed to one side of the axis of the leg 33 with the result that the left portion of the guide element 13, as viewed in FIG. 4, tends to move downwardly thereby constantly urging the tapered portion 37 of the finger 36 into engagement with the hold-down device 12.

It is further to be noted from FIGS. 5 and 6 that the portion 38 of the hold-down device 12 is of a generally inverted L-shaped cross section and that the tapered portion 37 of the guide finger 36 meets therein. In FIG. 7 there is illustrated a slightly modified form of the end portion of the guide finger, which end portion is of a tapered construction as is the end portion 37, but is of a cross section other than the circular cross section illustrated in FIGS. 5 and 6. The guide finger end portion of FIG. 7 is generally identified by the numeral 43 and is of a tear drop shaped cross section with the pointed end thereof extending upwardly. The hold-down device 12 is also provided with a modified cloth engaging portion 44 which, like the cloth engaging portion 38, is of an inverted L-shaped cross section, but wherein the upper leg thereof is provided with a longitudinally extending groove 45 of an arcuate cross section, the groove 45 cooperating with the pointed upper edge of the tapered portion 43.

Reference is now made to FIGS. 8, 9 and 10 wherein the details of the plunger or ridge forming disc 9 are shown. It is to be understood that the assembly of the ridge forming disc 9 includes a base element or frame 46 which is provided at the lower end thereof with a sleeve portion 47 adapted to be adjustably clamped onto a shaft 48. The base element 46 has a bifurcated upper portion 50 defining an upwardly opening slot 51 in which there is seated for guided vertical movement a plunger element 52. The plunger element 52 is pivotally mounted at one end thereof on a pin 53 which extends transversely of the slot 51 and which is suitably retained in place by being threaded within the base element for example.

It is also to be noted that the plunger element 52 is provided with an arcuate slot 54 which has received therein a further pin 55 which extends transversely of the slot 51 and which may be secured in the base element 46 as by being screw threaded therein. The pin 55 limits the range of vertical pivoting of the plunger element 52 with respect to the base element 16.

The base element 46 is also provided with a vertical bore 56in which a spring 57 is mounted. The upper end of the spring 57 bears against a ball 58 which, in turn, reacts against the lower edge of the plunger element 52 to constantly urge the same upwardly. The lower end of the bore 56 has adjustably threaded therein a screw 60 for varying the compression of the spring 57 and thus vary the resistance of the plunger element 52 against pivoting into the slot 51.

OPERATION Referring once again to FIGS. 5 and 6, it will be seen that the cloth which is being hemmed, the cloth being identified by the numeral 61, has an edge portion thereof doubly reversely folded into a generally S- shaped configuration with the hem portion including a first return fold 62 and a second return fold 63. The return fold 62 underlies a free edge portion 64 of the cloth 61 while the return fold 63 overlies the main body of the cloth. It is further to be noted that the return fold 63 has received therein the guide finger 36 with the tapered end portion 37 thereof supporting the cloth of the second fold 63 in constant engagement with the hold-down device 12, and more particularly with the end portion 38 thereof.

In timed relation, the plunger 8 moves upwardly and clamps a portion of the cloth 61 disposed adjacent the fold 63 against the underside of the hold-down device 11. At the same time, the needle 35 is moving transversely of the hold-down device 11 just beyond the free end thereof, and as a ridge 65 is formed in the cloth 61, the needle 5 pricks the cloth 61 and passes therethrough towards the plane of the hold-down device 12.

After the cloth 61 has been pricked by the needle 5 in the temporarily formed ridge 65 thereof, the plunger 8 moves downwardly while the plunger 9 moves further upwardly with the plunger element 52 clamping the folded cloth both between the plunger element 52 and the guide finger 36 and between the guide finger end portion 37 and the end portion 38 of the hold-down device 12. When the cloth has been so elevated, the nee dle 5 passes beyond the extreme end of the end portion 38 and pricks the uppermost fold of the cloth immediately above the guide finger end portion 37 as is shown in FIG. 6.

It is to be understood that the movement of the plunger element 52 upwardly is limited by the holddown device 12 whose upward movement, in turn, is limited by engagement of the adjusting screw 23 on the presser plate 7. It thus will be readily apparent that the uppermost position of the end portion 37 of the guide finger 36 may be accurately set for the pricking of the folded material supported by the guide finger 36 by the needle 5.

Although only a preferred embodiment of the invention has been specifically illustrated and described herein, it is to be understood that minor variations may be made in the cloth made in the cloth supporting mechanism without departing from the spirit and scope of the inventon, as defined by the appended claims.

I claim:

1. ln a blindstitch sewing machine for blind hemming a double reversely folded edge of material wherein a plunger delivers the folded material to a needle of the sewing machine; guide member means for extending into a fold of material being hemmed and supporting the material for the passage of the needle through the material.

2. The blindstitch sewing machine of claim 1 wherein said guide member means is in the form of a finger, said blindstitch sewing machine includes a presser foot, and there are mounting means yieldingly mounting said guide member means on said presser foot.

3. The blindswitch sewing machine of claim 1 wherein said blindstitch sewing machine includes a presser foot, means mounting said guide member means on said presser foot for relative swinging movement in a generally vertical plane, and said guide member means having a generally horizontal pivot axis positioned wherein said guide member means is gravity urged to an operative position.

4. The blindstitch sewing machine of claim 3 wherein a material hold-down opposes said guide member means and cooperates therewith to position and support material during a hemming operation.

5. The blindstitch sewing machine of claim 4 together with means carried by said presser foot for resiliently urging said material hold-down towards said guide member means, and said guide member means being resiliently urged by said material hold-down in opposition to the gravitational urging of said guide member means to an operative position.

6. The blindstitch sewing machine of claim 5 wherein the means for resiliently urging said material holddown towards said guide member means includes adjustable resilient means reacting on said material holddown.

7. The blindstitch sewing machine of claim 4 wherein said material hold-down is of an inverted L-shaped cross section and defines a seat receiving said guide member means.

6. The blindstitch sewing machine of claim 3 wherein said blindstitch sewing machine includes a stitching zone, and said guide member means extends into said stitching zone.

9. The blindstitch sewing machine of claim 3 wherein said needle is a curved needle having a path of movement generally parallel to said presser foot, and said guide member means includes a finger extending transversely of the path of needle movement.

111. The blindstitch sewing machine of claim 3 wherein said guide member means is formed of wire and has four legs arranged in a generally rectangular configuration, two of said legs having free ends, one of said legs forming part of said means mounting said guide member means, and the other of said legs being in the form of a material supporting finger.

11. The blindstitch sewing machine of claim 10 wherein said one leg is received in sleeve means of said presser foot and functions as a pivot for said guide member means.

12. The blindstitch sewing machine of claim 1 wherein said plunger directly underlies said guide member means and is mounted for oscillatory movement.

13. The blindstitch sewing machine of claim 1 wherein said guide member means is in the form of a finger, said blindstitch sewing machine includes a presser foot, and there are mounting means yieldingly mounting said guide member means on said presser foot, said plunger directly underlies said finger and is mounted for oscillatory movement in a plane passing through both said finger and said plunger.

14. The blindstitch sewing machine of claim 1 wherein said guide member means is in the form of a finger, said blindstitch sewing machine includes a presser foot, and there are mounting means yieldingly mounting said guide member means on said presser foot, said needle moving in an arcuate path above and transversely of said finger.

15. The blindstitch sewing machine of claim 1 wherein said plunger is carried by a support having a bifurcated part, said plunger being seated within said bifurcated part and pivotally mounted adjacent one end for movement therein, resilient means carried by said support for urging said plunger out of said bifurcated part, and stop means engageable with said plunger to limit outward movement thereof.

16. In a blindstitch sewing machine for blind hemming a double reversely folded edge of material wherein a plunger delivers the folded material to a needle of the sewing machine; guide member means for extending into a fold of material being hemmed and sup- 

1. In a blindstitch sewing machine for blind hemming a double reversely folded edge of material wherein a plunger delivers the folded material to a needle of the sewing machine; guide member means for extending into a fold of material being hemmed and supporting the material for the passage of the needle through the material.
 2. The blindstitch sewing machine of claim 1 wherein said guide member means is in the form of a finger, said blindstitch sewing machine includes a presser foot, and there are mounting means yieldingly mounting said guide member means on said presser foot.
 3. The blindswitch sewing machine of claim 1 wherein said blindstitch sewing machine includes a presser foot, means mounting said guide member means on said presser foot for relative swinging movement in a generally vertical plane, and said guide member means having a generally horizontal pivot axis positioned wherein said guide member means is gravity urged to an operative position.
 4. The blindstitch sewing machine of claim 3 wherein a material hold-down opposes said guide member means and cooperates therewith to position and support material during a hemming operation.
 5. The blindstitch sewing machine of claim 4 together with means carried by said presser foot for resiliently urging said material hold-down towards said guide member means, and said guide member means being resiliently urged by said material hold-down in opposition to the gravitational urging of said guide member means to an operative position.
 6. The blindstitch sewing machine of claim 5 wherein the means for resiliently urging said material hold-down towards said guide member means includes adjustable resilient means reacting on said material hold-down.
 7. The blindstitch sewing machine of claim 4 wherein said material hold-down is of an inverted L-shaped cross section and defines a seat receiving said guide member means.
 8. The blindstitch sewing machine of claim 3 wherein said blindstitch sewing machine includes a stitching zone, and said guide member means extends into said stitching zone.
 9. The blindstitch sewing machine of claim 3 wherein said needle is a curved needle having a path of movement generally parallel to said presser fOot, and said guide member means includes a finger extending transversely of the path of needle movement.
 10. The blindstitch sewing machine of claim 3 wherein said guide member means is formed of wire and has four legs arranged in a generally rectangular configuration, two of said legs having free ends, one of said legs forming part of said means mounting said guide member means, and the other of said legs being in the form of a material supporting finger.
 11. The blindstitch sewing machine of claim 10 wherein said one leg is received in sleeve means of said presser foot and functions as a pivot for said guide member means.
 12. The blindstitch sewing machine of claim 1 wherein said plunger directly underlies said guide member means and is mounted for oscillatory movement.
 13. The blindstitch sewing machine of claim 1 wherein said guide member means is in the form of a finger, said blindstitch sewing machine includes a presser foot, and there are mounting means yieldingly mounting said guide member means on said presser foot, said plunger directly underlies said finger and is mounted for oscillatory movement in a plane passing through both said finger and said plunger.
 14. The blindstitch sewing machine of claim 1 wherein said guide member means is in the form of a finger, said blindstitch sewing machine includes a presser foot, and there are mounting means yieldingly mounting said guide member means on said presser foot, said needle moving in an arcuate path above and transversely of said finger.
 15. The blindstitch sewing machine of claim 1 wherein said plunger is carried by a support having a bifurcated part, said plunger being seated within said bifurcated part and pivotally mounted adjacent one end for movement therein, resilient means carried by said support for urging said plunger out of said bifurcated part, and stop means engageable with said plunger to limit outward movement thereof.
 16. In a blindstitch sewing machine for blind hemming a double reversely folded edge of material wherein a plunger delivers the folded material to a needle of the sewing machine; guide member means for extending into a fold of material being hemmed and supporting the material for passage of the needle through the material, a support, means mounting said guide member means on said support for relative swinging movement in a generally vertical plane, and said guide member means having a generally horizontal pivot axis positioned whereby said guide member means is gravity urged to an operative position. 